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<b>let </b><font color="Maroon" title="c1">X1</font>, <font color="Maroon" title="c2">X2</font>, <font color="Maroon" title="c3">Y1</font>, <font color="Maroon" title="c4">Y2</font> be    <a href="hidden.html#M1" title="HIDDEN:mode.1">set</a> ;<br/>







<b>assume </b><a NAME="E1:84"/><i><font color="Green" title="E36">A1</font></i>: 
( <font color="Maroon" title="c1">X1</font> <a href="tarski.html#R1" title="TARSKI:pred.1">c=</a> <font color="Maroon" title="c2">X2</font> &amp; <font color="Maroon" title="c3">Y1</font> <a href="tarski.html#R1" title="TARSKI:pred.1">c=</a> <font color="Maroon" title="c4">Y2</font> )
 ;<br/>

<b>let </b><font color="Maroon" title="c5">f</font> be    <a href="hidden.html#M1" title="HIDDEN:mode.1">set</a> ; <i><font color="Red">:: according to </font></i><a class="ref" href="tarski.html#D3" title="TARSKI:def.3">TARSKI:def 3</a><br/>

<b>assume </b><a NAME="E2:84"/>
<font color="Maroon" title="c5">f</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a>  <a href="partfun1.html#K4" title="PARTFUN1:func.4">PFuncs</a> <font color="Maroon" title="c1">X1</font>,<font color="Maroon" title="c3">Y1</font>
 ;<br/>

<a NAME="E3:84"/><b>then </b>
<font color="Maroon" title="c5">f</font> is   <a href="partfun1.html#NM1" title="PARTFUN1:NM.1">PartFunc</a> of <font color="Maroon" title="c1">X1</font>,<font color="Maroon" title="c3">Y1</font>
 
<b>by </b><i><a class="ref" href="partfun1.html#T120" target="_self" title="PARTFUN1:th.120">Th120</a></i>;<br/>
<a NAME="E4:84"/><b>then </b>
<font color="Maroon" title="c5">f</font> is   <a href="partfun1.html#NM1" title="PARTFUN1:NM.1">PartFunc</a> of <font color="Maroon" title="c2">X2</font>,<font color="Maroon" title="c4">Y2</font>
 
<b>by </b><i><a class="txt" href="partfun1.html#E1:84"><i><font color="Green" title="E36">A1</font></i></a>, <a class="ref" href="partfun1.html#T32" target="_self" title="PARTFUN1:th.32">Th32</a></i>;<br/>
<b>hence </b><a NAME="E5:84"/>
<font color="Maroon" title="c5">f</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a>  <a href="partfun1.html#K4" title="PARTFUN1:func.4">PFuncs</a> <font color="Maroon" title="c2">X2</font>,<font color="Maroon" title="c4">Y2</font>
 <b>by </b><i><a class="ref" href="partfun1.html#T119" target="_self" title="PARTFUN1:th.119">Th119</a></i>;<br/>


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